There is well known a vehicle provided with a fluid-operated power transmitting device provided with a lock-up clutch and configured to transmit a drive force of an engine to drive wheels. Patent Document 1 discloses an example of such a vehicle. The above-indicated lock-up clutch is generally commanded to be selectively placed in its engaged and released states, on the basis of a running state of the vehicle and according to a relationship predetermined for the purpose of improving fuel economy of the vehicle. For example, a lock-up control of the lock-up clutch is initiated when the running state of the vehicle falls within a lock-up control region. Further, the lock-up control region can be enlarged to improve the fuel economy, by implementing a slip control of the lock-up clutch (a lock-up slip control or flexible lock-up control) wherein the lock-up clutch is given a suitable amount of slipping on the basis of the vehicle running state and according to the above-indicated predetermined relationship, so as to permit a lock-up action of the lock-up clutch over a wide range of the vehicle running state. For instance, the Patent Document 1 proposes a vehicle starting slip control of the lock-up clutch (vehicle starting slip control or flexible vehicle starting control) to improve the fuel economy, by controlling a slipping state of the lock-up clutch so as to positively bring the lock-up clutch in its engaged state during starting of the vehicle with the engine operated as a vehicle drive power source, for thereby reducing a rise of an operating speed of the engine (reducing an amount of racing of the engine).